This is a bug we’re currently working on fixing. We do have a workaround however.
Make sure you do this in google chrome since this is the most compatible browser for SmartSite.

(I’ve attached screenshots for each step)

Step 1: Right click the home page photograph and select inspect element.
Step 2: Make sure you have the grey highlighted line selected, and uncheck the box circled in red.
Step 3: You should now be able to click the main image and change the photo.